Source : Webster's Revised Unabridged Dictionary (1913)

Polycystina \Pol`y*cys*ti"na\, n. pl. [NL. See {Poly-}, and
   {Cyst}.] (Zo["o]l.)
   A division of Radiolaria including numerous minute marine
   species. The skeleton is composed of silica, and is often
   very elegant in form and sculpture. Many have been found in
   the fossil state.